Beverton and Holt’s yield per recruit model

Ganga, U (2017) Beverton and Holt’s yield per recruit model. In: Course Manual Summer School on Advanced Methods for Fish Stock Assessment and Fisheries Management. Lecture Note Series No. 2/2017 . CMFRI; Kochi, Kochi, pp. 228-231.

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Abstract

Yield per Recruit (Y/R) is the expected life time yield per fish recruited into the stock at a specified age. The Beverton and Holt’s Yield per Recruit model (1957), is a predictive model that can be used by fishery managers to understand the biological / economical effect of fishing on the stocks and helps them to take suitable measures to ensure sustainable yields from the fishery. In the Beverton and Holt (1957) yield equation, the response of a population to fishing mortality on a per-recruit basis depends on natural mortality (M), fishing mortality (F),growth rate (K, from the von Bertalanffy growth equation) and the age (tc) at first capture (depends on gear selectivity). A fishery manager will aim at arriving at a combination of measures that will ensure that the fish stocks are exploited at such a level that there is neither growth nor recruitment overfishing, and predictive models employing the Y/R concept enable these decisions. Maximum yield from a cohort can be realised only by exploiting it at an age or size (optimum age or length) at which the cohort’s biomass reaches its maximum. Thus, ideally fishery managers should be implementing exploitation strategies that do not harvest fish too early (by restricting catches of juvenile fishes) or too late when most of them would die due to “senility” or similar reasons operated through natural mortality.

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